The Birdy is a full suspension folding bike, which means that other than offering a comfortable ride through the suspension, it also has to fold down to a reasonable size.
In the earlier post, I documented how the stock Birdy City folds, and what are some of the considerations to take note of during folding. I also compared the folded size to the Fnhon DB12, as well as some of the bike geometry.
After the modifications, I have learnt a lot more about the quirks of the Birdy, especially during folding. Here are some of my findings and observations, for you to take note of if you plan to get a Birdy or do any modifications.
Starting with the front suspension fork, one of the challenge is to route the front brake hose neatly and robustly, so that it can withstand folding without damage or interference. I experimented with many different routes and also consulted many online sources to see how other people do it.
Most dealers use mechanical brake calipers or hybrid mechanical/hydraulic brake calipers, where the hydraulic caliper is actuated by a standard steel brake cable. This solves the problem of bending or stretching the brake outer casing when the fork is folded.
On the other hand, there are a few successful examples where a full hydraulic hose routing is done, and seemingly with no major issues. This is definitely my preference as I much prefer the feel of the hydraulic brake levers.
The objective is to route the hydraulic hose in a way that it does not get kinked or twisted excessively when folded, during the folding process and when fully unfolded.
After many trials with a spare hydraulic hose, I finally found something that works. The free length, fixed length (with cable tie) and curvature of the hose are all factors that determine whether the hose can move freely during folding.
Final routing, with the hose running on the inside of the fork, using a cable tie to fix the position. The direct hose connection to the XTR brake caliper matches this routing well.